There's all kinds of problems with this argument.
One book (Goldsmith and Owen) argues that,
using the same logic, ballpoint pens must be
made by aliens, since 1,000,000,000,000
times the size of a ballpoint pen gives
exactly 149,600,000 km -- the distance
between the Earth and the Sun.
More importantly, I think, is the insulting
implication that the ancient Egyptians
were not smart enough to have known how to
build the pyramids, and therefore aliens must
have done it.